Inductor for the heat treatment of workpieces, especially crankshafts



SEULEN 2,665,367 THE HEAT TREATMENT C ECIALLY G. W. INDUCTOR FOR OF WORKPIE ES, ESP CRANK-SHAFTS Jan. 5, 1954 3 Sheets-Sheet 1 Filed June 8. 1949 iNVEN TOR $584420 M 55/150.

ORNEYS CIALLY CRANKSHAFTS Filed Jun 8 9 3 Sheet 5 2 I lli lllmumu i M 1% m II" "ll NI INVENTOR 95mm? 55015,

A ORNEYS G. w. SEULEN 2,665,367 INDUCTOR FOR THE HEAT TREATMENT OF WORKPIECES, ESPE Jan. 5, 1954 HEAT TREATMENT OF WORKPIECES, ESPECIALLY CRANKSHAFTS Filed June 8, 1949 e. w. SEULEN 2,665,367 INDUCTOR FOR THE 3 Sheets-Sheet 3 INVENTOR 956M 20 M SfZ/Af/V QRNEYS Patented Jan. 5, 1954 INDUCTOR FOR THE HEAT TREATMENT OF WORKPIECES, ESPECIALLY CRANK- SHAFTS Gerhard W. Seulen,

Remscheid, Germany, as-

signor to Deutsche Edelstahlwerke Aktiengesellschaft, Krefeld, Germany, a corporation of Germany Application June 8, 1949, Serial No. 97,847

Claims priority, application Great Britain June 18, 1948 10 Claims.

The heat treatment of steel, for instance, for the purpose of surface hardening, is usually carried out by inductive devices whose loop conductors are connected to a transformer which supplies the required current of low tension and high current density. When such inductors are used for the heating of work pieces that are not bordered by shoulders or other projections, it is not necessary to subdivide the inductor because it can be placed onto the work piece without difficulty. However, if the work piece to be treated has shoulders or projecting portions of relatively large dimensions, the inductor must be subdivided in order to permit placing it onto the work piece portion to be treated. In this case, the inductor is generally composed of two half portions which during the treatment of the work piece are held together by suitable fastening means.

This, for instance, is the case when treating crank shafts, cam shafts, crank pin and similar parts which are to be hardened and whose pins to be treated are bordered by the hubs, bosses or cams of the shaft. As far as the heating performance is concerned, the just-mentioned subdivided inductors are well proven in practice. However, if work pieces or zones of difierent dimensions are to be treated, it is necessary to provide inductors of correspondingly difierent dimensions so that a special inductor of suitable shape and size is available for each of the zones of the work piece to be heated.

In order to treat the various parts of crank shafts, as many hardening stations must be provided as the crank shaft has pins of different dimensions. For instance, if a crank shaft for a diesel engine has six eccentrically located crank pins and seven centric bearing pins and if all of these pins are to be hardened, as much as five to seven treating stations are needed because the crank pins have dimensions different from those of the intermediately located bearing pins, and the various bearing pins may also have respectively different dimensions. After the six eccentric crank pins have been hardened in the first station, the first bearing pin is treated in the second station, the second to fifth bearing pins in the third station, the third bearing pin in the fourth station, and the fourth to seventh bearing pins in the fifth station, etc. The number of the required treating stations is determined by the number of the bearing and crank pins of respectively different dimensions.

Since the treating equipment must be designed for the most unfavorable case of application, it

is generally necessary to provide seven treating stations. Each of these stations may be connected through a transformer and a suitable switch to a common generator, and suitable control devices may take care that only one of the stations is connected with the generator at a time.

As apparent from the foregoing, a rather large and intricate installation is necessary for this kind of heat treatment for the surface hardening of crank shaft pins and similar work pieces. The exchange of the various inductors is time-consuming and complicated so that, with the cusinductors, a considerable disadvantage must be put up with when using induction heating and hardening equipment.

It is an object of my invention to devise an inductor for achieving a considerable reduction in the cost of the equipment and making it unnecessary to move the work piece from one hardening station to the other so that the time required for the complete hardening treatment is also reduced. It is also an obiect of the invention to make an inductive heating device applicable for work piece zones of difierent dimensions and shapes while using for the various zones a single inductor base member whose connections to the current supply circuit need not be changed when adapting the inductive device to the various zones or Work pieces.

In order to achieve these cordance with my invention,

objects, and in ac- With each other to form together a loop around One of these members, hereinafter called the "base member, has two mutually insulated parts or rails to be connected to the respective two poles of the energizing transformer or other current source. The width of this base member in the axial direction of the work piece is adapted to the smallest width of the work piece portion to be treated. The second member of the inductor, hereinafter called the cap is removably connected with the base member and has it width and diameter adapted to any other portion of the work piece to be treated.

According to another feature of the invention, a plurality of differently dimensioned cap members are provided adapted to the respectively different work pieces or zones to be treated; and

any one of these cap members can be selected.

for attachment to a single base member.

ihese and other objects and features of the invention will be apparent from the'following description in coniunction with the embodiments exemplified by the drawing, in which Figure l is a schematic side view and Fig. 2 a front view of an inductor according to the in vention;

Fig. 3 is a partiallv schematic side view and Fig. 4 a front view of another inductor according to the invention;

Figs. 5 and 6 represent schematically a side view and front view, respectively, of a third inductor according to the invention;

Fi s. '7 and a are side and front views, respectively, of another embodiment. and

Fi s. 9 and 10 are schematic illustrations of two respective other modifications of inductors according to the invention.

Figs. 1 and 2 elucidate schematically the design and operating principle of inductors according to the in ention. A portion of a work piece W, for instance. a crank p n, is to be treated. The inductor for heating the crank pin is composed of a b se member A and a cap member 33. The width oi base member A, measured in the axial direction of the shaft. is so ch sen that it is not larger than the width of the shortest shaft'por ticn or pin to be treated. Member A is composed of two conductive parts or rails that are rigidly W interconnected but insulated from each other as is shown at d. lhe two rails are'to be connected to the respective poles of a transformer or other source of alternating current of the suitable freouencv, for instance, radio frequency. The cap member B is of arcuate shape and has two flange portions in engagement and electric contact with the two rails of the base member A to which it is removablv attached. The inner diameter and the width of cap member B are in accordance with those areas of the work piece portion to be treated that are outside theeifective range of member A. Generally, the base member A of the inductor acts the center area and the cap member B on the adjacent outer areas of the work piece portion. For instance, when the crank pin to be treated has a diameter of 10 cm. and a width of about lO'crn., the same inductor base member of about 5 cm. width can be used as for a pin of only 5 cm. diameter and 5 cm. h. Only the cap member B is'different for crank pins of different dimensions. In the firstmentioned case, member B has an overall axial width of about 10 cm. and an inner diameter of about 10 era. while in the second case member B of the inductor has a width of about 5 cm. and an inner diameter of about 5 cm. The inst-men'- tioned numerical values are approximate because the necessary tolerances between the surfaces of the work. piece and the surfaces of the heatin inductor. of course, are to be considered. During the heating, the work piece W is kept revolving about the axis of the portion to be treated in order to secure an even distribution of the temperature.

It will be recognized that the flange portions of cap member B which contact the member A are interconnected by the heating conductors C proper. In the embodimentof Figs. 1 and 2, two such conductors C extend in paralle relation to each other on either side of the range of base member A. As a rule, the conductors are so disposed and dimensioned as to secure a desired heat distribution in the treated zone of the Work. piece, for instance, so that the temperature in the surface portion of the treated piece is distributed in a predetermined manner. To this end, the heating conductors may have difierent shapes and may extend at different or varying angles relative to the axial direction of the crank pin, as will be understood from the embodiment described in a later place with reference to Figs. 5 and 6.

It is generally desirable to lreep the gap between the inductor and the surface of the work piece as narrow as possible. When using the same base member A for work pieces or zones of different diameters, the gap between base memher and work pieces, of course, will differ. In order to reduce this difference, the surface area of the'base member facing the work piece is preferably curved, for instance, in the manner shown at D in Fig. 1.

In the embodiment according to Figs. 3 and i, the'base member A1 of the inductor is composed of two flat copper rails c1 and (is which are insulated from each other at d for connection to the respective poles of the power transformer or other current source. The r ils c and an are disposed at an angle of relative to each other, i. e. their surfaces facing the work piece are aligned within a common plane.

The upper portion of Figs. 3 and 4 show the inductor equipped with a removable cap member b for the treatment of a crank pin of large diarni eter and large axial width, while the lower half of the same illustrations shows a cap mu. her for treating a pin of smaller diameter and smaller width. Each cap member has two heatirc, conductors b1 and. 722 (Fig; 4) extending parallel to each other between flange portions f1 and f2. Clamping devices G connect the cap member with the base member under pressure applied, for instance'by means of a clamping eccentric. In order to secure a proper position of the two inductor members relative to each other, the base member is equipped with guiding lugs During the treatment, the portions of the work piece to be treated revolve in the direction of the arrow J. The work piece portion is centered by means of guiding rollers K of nonmagnetic material.

It is usually desirable to cool the inductor with water. To this end, the inductor members are preferably hollow and have ducts for the cooling water extending along the path apparent from the arrows L which indicate the flow direction of the water. As apparent from these arrows, the water enters into the rail or and flows through the conductors in and b2 to the rail as. If an intensive cooling is required, a separate flow of water can be sup-plied through each'of the copper rails a1, a2 whence it flows through only one-half of part h before it leaves the inductor. The connections through which the water flows from the base member to the cap member of the inductor is tightened by gaskets which are subjected to the high clamping pressure between the two inductor members.

The inductor current flows in the direction of the arrows M. The heat distribution is influenced simply by selecting the width N (Fig. 4) of the heating conductors b1, ha of the cap memher. A large width of these conductors produces an'increased heat intensity in the middle area of the work piece, while a reduced width of the heating conductors increases the heat intensity in the outer sections of the work piece portion under treatment.

When using the inductor for the purpose of surface hardening, it is desirable to provide a suitable quenching device for quenching the surface after it has reached the hardening temperature. These quenching devices may be disposed at the side of inductor base member. However, these devices may be additionally or exclusively arranged at the cap member between the conductors in and b2. In this case, the cap member of the inductor is equipped with a supply line for the quenching water. However, the water may also be supplied through the base member and through openings in the contact surfaces between base member and cap member. The loop member is equipped with a handle (not shown) to facilitate exchanging it after each treatment.

In the embodiment shown in Figs. and 6, the two copper rails as and at of the base member A2 extend at an angle of 90 relative to each other. The corner portion, at o, of the angular design is shaped to reduce the air gap between work piece W and base member A2. Two of the guide rollers K in this embodiment a 'e journalled on the base member while only one of them is mounted on the removable loop member B. The two inductor members are joined together by means of bolts P which are rigidly secured to member B and traverse respective bores P1 in member A2 of the inductor. In the rear portion of the inductor, the bolts P are pulled magnetically, mechanically or hydraulically by suitable pressure means (not illustrated) in order to secure a satisfactory contact pressure. The guide rollers K of the base member are preferably displaceable in the direction of the arrows Q in order to adjust these rollers for diiierent diame ters of the work pieces to be treated. The contact surfaces of the inductor members may be serrated as shown at R1, R2, in order to improve the contact between members A2 and B.

Instead of two parallel connected heating conclusters as described previously, the part B of the inductor shown in Fig. 6 has only a single heating conductor which extends between terminal bars f3 and ft. The terminal bars are joined with the t respective flanges of cap member B. This design permits controlling and varying the heating zone as desired by a corresponding selection of the width and arrangement or" the heating conductor.

In the embodim nt according to Figs. 7 and 8, the base member of the inductor is substantially semi-circular and composed of two arcuate rails [is and 05s. This permits a considerable reduction of the air gap for all diameters of the work pieces to be treated. In order to secure a suffi-- cient pressure at the electric contact surfaces and the connecting joints of the water ducts, the inner surfaces of parts as and as may have a stepped design as indicated at Y, or these surfaces may have grooves T engageable by a corresponding projection T of member B.

The cap member B of the inductor is held under pressure against the steps or notches by means of bolts P2 and P3. A pulling force in the direction of the arrows P is applied to these bolts by suitable mechanical hydraulic or pneumatic means, It will be understood that the upper half of Figs. '7 and 8 shows the inductor app-lied to a work piece portion of large diameter, while the lower half of these figures shows the inductor applied to a work piece of small diameter.

Because of the electric or coolant supply lines, it is sometimes difficult to accommodate the guide rollers. It is, therefore, often desirable to depart from the substantially symmetric design of the inductors according to Figs. '1 through 8, while, of course, maintaining a symmetric triangular arrangement of the guide rollers. This is exemplified by the device shown in Fig. 9. In this device, two guide rollers K are mounted on the removable cap member 13 of the inductor, while the third roller K is mounted on the base member. The two rails a of the base member are aligned with each other but have diiierent lengths, and the roller K is mounted on the longer one of the two rails. In the embodiment of Fig. 10, the rails of the inductor base men her are of arcuate shape. The appertaining terminal or bus portions M for supplying current are bent, and one of the guide rollers K is disposed at about the center of one or the arcuate rails a, while the remaining two rollers K are mounted on the removable loop member of the inductor. It is also possible to have the rails a extend at a right angle to each other and to dispose the appertaining one roller K near the point of the angle. It is obvious that various other modifications of design and shape are applicable in order to secure a simple and favorable arrangement of the guide rollers.

The invention is not limited to the illustrated and specifically described embodiments. For instance, the efficiency can be improved by arranging magnetic yokes on the inductors or the appertaining heating conductors, and the various features of the invention can be combined with one another in a manner different from the specific embodiments here disclosed. The shape of the inductors may be changed in order to adapt them to work pieces different from those mentioned in the foregoing.

I claim:

1. An inductor device for heat treatin workv pieces, in particular crank shafts, comprisi' g an inductor base member having two conductive rails rigidly joined with each other, each of said rails being of generally angular shape and having two angle legs of which one extends parallel and adjacent to the corresponding leg of the other rail, insulation disposed between said parallel legs for electrically insulating rails from each other, said two other legs or respective rails being serially arranged with to each other and forming together tially continuous surface facing the when the device is in operative con 1 said other legs having respective end flanges re mote from each other, an arcuate member ing a heating conductor portion of substantially horseshoe-shaped axial elevation and having two ends angularly and outwardly pro rt said conductor portion in a plane pa of the horseshoe shape, said ends b tact engagement with said respec" when said device is in said condition, ar

i1 ate member forming in series with said two ot'ie legs of said respective rails a closed loop around having a loop opening of larger size than the cross section of the work piece to be treated and of an irregular shape compared with a circle, and releasable fastening means connecting said respective ends with said flanges to permit exchanging the arcuate member.

2. An inductor device for heat treating work pieces, in particular crank shafts, comprising an inductor base member having two serially adjacent conductive rails rigidly joined. with each other and electrically insulated from each other for connection to a current source, said rails having respective flange portions extending away from .each other, a plurality of arouate members each having a conductor portion of substantially horseshoe-shaped axial elevation and two end portions, said conductor portions of said respective arcuate members having different dimensions including diiierei t arouate widths so that said two end portions of different respective arcuate members are difierentl'y spaced from each other, said two flange portions of said respective rails having respective seating surfaces each having a plurality of mutually adjacent seat areas engageable with the end portions of arouate members of respectively different widths, whereby said different arouate members are selectively joinable with said base member and to form together with said base member an inductive loop around the workpiece axis, said loop having a loop opening of larger size than the work-piece cross section to be treated and of a shape departing from a circle. 4

S. An inductor device for heat treating work pieces, in particular crank shafts, comprising an inductorbase member having two serially adja cent conductive rails ri idly joined with each other and electricallyinsulated from each other for connection to a current source, an arcuate member exchangeably secured to said base memher and having two flange portions and two substantially horseshoe-shaped heating conductors, said conductors being mutually spaced and extending parallel to each other between said two flange portions, said flange portions being in face-to-face engagement with said respective rails and said arouate member forming together with said rails a loop aroundthe work-piece axis when the device is in operation.

4. In a device according to claim 1, said two rails having respective current supply buses integral with said two parallel legs respectively, and said two other legs having different respective lengths so that said two supply buses lie out of center relation to said surface.

5. An inductor device for the heat treating of crankshaits and similar axially elongated work pieces, comprising an inductor base structure having two metal rails with respective electric terminal means for connection to a current source, said rails being insulatingly and rigidly joined with each other and extending in opposite directions away from their junction, said rails having respective longitudinal surfaces extending in said respective directions and forming each a continuation of the other, an arcuate con ductor member removably mounted on said base and electrically interconnecting said rails, said member having transversely to said surfaces a larger width than said base structure and comprising a middle portion of partly semi-circular shape adapted to straddle the work piece and two end flanges integral with said middle portion, saidrlanges being seated on said respective surfaces on both sides respectively of said junction, said member forming together with the portion of said base structure between said two flanges a closed'inductive loop within an elevation plane longitudinal of said rails and perpendicular to said surfaces so as to be capable of peripherally surrounding the work piece relative to a radial plane thereof, and said loop having an inner opening larger than the largest work-piece cross section to be treated and of a shape departing from a circle.

6. In a device according to claim 5, said rails having curved shape and forming together a sub-- stantially concave surface at the side of the work piece to be treated, and said arouate memher being curved away from said surface.

7. In a device according to claim 5, said rails having arouate shape and forming together a substantially concave surface at the side of the work piece to be treated, said rail portions hav ing stepped grooves disposed at said surface, and said arouate member being engageable with said grooves of said respective rail portions.

8. In a device according to claim 5, said middle portion of said arcuate member consisting essentially of a single conductor having in a direction transverse to said surfaces a thickness smaller than the width of said member, said conductor extending from one transversal side of one of said end flanges to the opposite side of said other end flange.

9. An inductor device according to claim 2, comprising roller means engageable with the work piece to guide it for revolution during heating, part of said roller means being mounted on said base member, and part of said roller means being mounted on each of said arouate members.

10. In a device according to claim 5, said two rail surfaces extending at an obtuse angle to each other, and said arouate member being curved away from the point of said angle.

GERI-IARD W. SEULEN.

References Cited in the file of this patent UNITED STATES PATENTS Nurnber Name Date 2,181,899 Kennedy Dec. 5, 1939 2,348,361 Rudd et al. May 9, 1944 2,395,196 Roberds Feb. 19, 1946 2,419,619 Wood Apr. 29, 1947 2,456,091 Stevens et al. Dec. 14, 1948 2,476,935 Wharff July 19, 1949 2,574,564 Hogelet al Nov. 13, 1951 OTHER REFERENCES Curtis, How to design coils for induction heating, American Machinist, January 31, 1946, pages -78. Copy in Scientific Library.

Griffith et al., Allis Chalmers Electrical Review, Second Quarter, 1948, page 15. (Copy available in Div. 3'7.) 

